A prominent lawyer who spent years fighting for the rights of lesbian, gay, bisexual and transgender people set himself on fire Saturday.

David S. Buckel's charred remains were found in a New York park, The New York Timesreported. In a letter Buckel emailed to the publication and other media outlets earlier that day, he wrote, "Honorable purpose in life invites honorable purpose in death."

A former marriage project director for Lambda Legal, a nonprofit organization that advocates for the rights of LGBT people, Buckel played a major role in a long, dark battle for recognition and equality.

In one of his most noted cases, he represented the mother of Brandon Teena, a transgender man who had notified a Nebraska sheriff that he had been raped. The sheriff informed Teena's assailants who killed him in the days that followed. "It should not be the case that reporting a crime makes matters worse for you," Buckel toldThe Daily Nebraskan in 2001. Eventually the sheriff was found liable for failing to protect Teena and his brutal murder was dramatized in a film called Boys Don't Cry starring Hilary Swank.

In 1996, Buckel represented an openly gay Wisconsin student who dropped out of high school after suffering prolonged physical and verbal bullying by peers, with no intervention by the school administration. In a landmark decision, the federal court ruled that the school should have prevented anti-gay harassment.

In 2006, he argued to the New Jersey Supreme Court that gay couples were not receiving equal protection of the law after municipalities them denied marriage licenses. As he embarked on the marriage equity case, he asked his future legal partner, "Do you want to be involved in the greatest civil rights movement of our time?"

Through his career, he stood up to the Boy Scouts of America, the U.S. military and the I.R.S., according to Cornell Law School, where he received his law degree. He also represented low-income and disabled people.

By 2016, Buckel was focusing on protecting the environment. As a senior organics recovery coordinator for an initiative hosted by the Brooklyn Botanic Garden, he wrote about how Brooklynites were composting food with the help of solar and wind energy.

On the last day of his life, he reportedly emphasized environmental responsibility, stating in a note to the media, "Pollution ravages our planet, oozing inhabitability via air, soil, water and weather. Most humans on the planet now breathe air made unhealthy by fossil fuels, and many die early deaths as a result — my early death by fossil fuel reflects what we are doing to ourselves."

It was a warm, sunny morning, and a Twitter account by Prospect Park had tweeted, "Host your child's next birthday party in Brooklyn's Backyard. Families can rent the Prospect Park Carousel for birthdays and special occasions."

The Times said that authorities had cleared away Buckel's body by 11 a.m., and a dark, circular patch was left in its place marked by two cones.

The New York City Police Department told NPR that a note was left at the scene. "It is being treated at the time as a suicide but it's still under investigation," a spokesperson said.

Camilla Taylor, Lambda director of constitutional litigation and acting legal director, said in a written statement, "We have lost a movement leader, a colleague, and a friend. We will honor his life by continuing his fight for a better world."